Today, most environmental problems facing society are attributed to the discharge of toxic chemicals susceptible to interact with the environment and to consequently exert some adverse effects on the ecosystem and human health. Pesticides constitute a group of chemical substances that are used for the control of unwanted organisms. The judicious use of these substances has allowed the society to prosper in many ways, however, their use has also resulted in new problems. Inorganic arsenicals (arsenic) and arsenic represent two examples of pesticides that have been applied in agricultural areas of Mississippi for crop protection. The available toxicological data on these two chemicals indicate that a number of significant works have already been done to assess their toxic effects to humans and laboratory animals. However, very limited and sometimes controversial information is published on their genotoxic effects and their toxicokinetics. Also, no data is available on their combined toxi city to humans and experimental animals. This research is proposed to assess the toxicokinetics, histopathology and in vivo genotoxic effects of arsenic and atrazine, using fish and rats as model test animals. The specific aims of this research are: 1) to determine the acute toxicity of arsenic, atrazine and arsenic-atrazine mixture to fish and rats; 2) to evaluate the toxicokinetics of arsenic and atrazine in fish and rats; 3) to conduct biochemical analyses to determine the effects of arsenic and at-razine on the activities of specific indicator enzymes; 4) to determine the genotoxic effects of arsenic and atrazine, by assessing the type and extent of chromosome aberrations, the mitotic index, and the DNA damage in rats; 5) to utilize the Microtox and the Mutatox Test Systems to determine the relative toxicities and the genotoxic potential of arsenic and atrazine; and 6) to conduct histopathological examinations to monitor the extent of tissue injury following chronic exposure of fis h and rats to arsenic and atrazine. All acute and chronic bioassays will be conducted following previously described/published test protocols. All experiments Mll be designed around the themes of toxicokinetics, acute, chronic and genotoxicity of arsenic and atrazine. It is expected that the results of this research will significantly contribute to new scientific knowledge on the toxicology of arsenic and atrazine.